A method in which the brush portion is moved reciprocatively in parallel to the tooth row is most popularly adopted when teeth are brushed while operating a toothbrush by a hand. Also in case of power-operated toothbrushes, reciprocatory motions alone are performed by the brush and only the surface portion of the tooth row is brushed. Namely, the interior of the gingival groove between the tooth and gingiva, where dental dirts are readily deposited, is hardly cleaned.
As the result of researches, it was found that in order to remove dental dirts, food remains and other foreign substances from narrow dents such as gingival grooves, good results are obtained when top ends of hair of a toothbrush are inserted into the gingival grooves and the base portions of the hairs are turned with the top ends of the hairs being as fulcrum to impart to the top ends of the hairs such forces that the top ends of the hairs are caused to dig out foreign substances from the gingival grooves and spatter them out of the gingival grooves spirally, and it was also found that for removal of foreign substances such as mentioned above, which are stuffed between adjacent tooth neck surfaces, reciprocatory motions of the brush along these adjacent tooth neck surfaces are very effective.